I posted that to show that the benefit of the higher MPG is small, but if people want to go after it, that is their choice, and many people like a challenge.

I would guess that rubbery parts
.... hoses, seals, vacuum lines
would have their service life shortened
by increased temperatures.

I would guess that aluminum to cast iron junctions,
like cylinder heads, manifolds
would be most likely to warp at higher tempertures.

I would not think that cast iron against cast iron parts would be affected much.

Since bore wall wear goes down with increased coolant temperature
(Continental Motors research)
I would guess that maybe piston ring wear would go down too.

Much of this bore, ring and piston wear
is from acids that are best kept as vapor,
never as a liquid (electrolyte allows corrosion)
so higher temperatures that are above the mixture's boiling temperature reduce corrosion.
Similar to 50/50 anti-freeze and sea water,
these mixtures of acids in water boil at temperatures above 212 F.

Continental Motors now mainly makes aircraft gasoline engines, and I for one was sad to see the press release last month where they were sold to a Chinese company.